In the processing of petroleum, the petroleum reforming operation involves the use of reformer tubes which can be heated to temperatures in excess of 2000.degree. F. In time, the creep that is induced by these high temperatures can cause the reformer tubes to fail. It is important that reformer tubes be replaced before they fail because failure of a tube during the reforming process can cause serious adverse consequences to the processing plant. Cracking tubes and other tubes used in various industrial processes are subject to the same problems.
In the past, it has been common practice to inspect reformer tubes through the use of ultrasonic techniques. However, ultrasonic inspections have not always succeeded in detecting reformer tubes that are on the verge of failing, and the reliability of the inspection procedure has suffered accordingly.